Exogenous application of silicon at the boot stage decreases accumulation of cadmium in wheat (Triticum aestivum L.) grainsBraz. J. Bot


Iqbal Hussain, Muhammad Arslan Ashraf, Rizwan Rasheed, Anum Asghar, Muhammad Asim Sajid, Muhammad Iqbal
Plant Science


Max born medal and prize

The Institute of Physics

Soil and Plant Responses to the Application of Ascophyllum nodosum Extract to No-Till Wheat ( Triticum aestivum L.)

Avijit Sen, V. K. Srivastava, Ram K. Singh, A. P. Singh, P. Raha, A. K. Ghosh, N. De, A. Rakshit, R. N. Meena, Ashok Kumar, Om Prakash, M. K. Ghosh, Marwan Manea, P. K. Upadhyay


Exogenous application of silicon at the boot stage decreases accumulation of cadmium in wheat (Triticum aestivum L.) grains

Iqbal Hussain • Muhammad Arslan Ashraf •

Rizwan Rasheed • Anum Asghar •

Muhammad Asim Sajid • Muhammad Iqbal

Received: 7 August 2014 / Accepted: 16 December 2014  Botanical Society of Sao Paulo 2015

Abstract A pot experiment was conducted to assess role of added silicon (Si) in alleviating cadmium-induced oxidative stress in wheat cultivars (AARI-2011, Cd-sensitive and FSD-2008, Cd-tolerant). Plants were exposed to different levels of CdCl2 (0, 25, 50, and 75 lM Cd/kg) along with sodium silicate (0 and 1.5 mM) at the boot stage.

Cadmium stress resulted in a marked decline in various growth attributes, photosynthetic pigments, and the activities of some enzymatic antioxidants, particularly in Cdsensitive wheat cultivar. Application of Si reduced Cdmediated oxidative stress and increased photosynthetic pigments and proline contents in both wheat cultivars.

Although Si application affected the shoot and grain Cd2? concentrations differently in both cultivars, it decreased

Cd2? concentrations in the grains in both wheat cultivars.

However, at higher Cd2? concentrations, Si was very effective in decreasing Cd2? concentrations in the grains of

Cd-tolerant cultivar. The alleviatory effects of Si on Cd2? concentrations in grain could be attributed to the altered

Cd2? uptake and translocation, particularly at higher Cd2? concentrations in both wheat cultivars. The effectiveness of

Si to reduce grain-Cd2? concentrations in diverse wheat cultivars suggested its use as soil amendments in the Cdpolluted environments.

Keywords Antioxidant enzymes  Cadmium 

Grain yield  Silicon  Wheat


Heavy metals are among major pollutants of the environment (Clemens 2006). Cadmium is toxic and among nonessential element for plant growth and development.

Therefore, higher concentration of cadmium in the growth medium suppresses plant growth. Cadmium is continuously added to the soil through different means including weathering, anthropogenic actions like urban runoff, extensive metal mining, composts, fertilizer application, and sewage sludge (Kirkham 2006). Cadmium severely affects human health (Stohs et al. 2000). High mobility of cadmium makes it most hazardous metal which is toxic even when present in small concentration (Sanita` di Toppi and Gabbrielli 1999). Mostly, Cd2? is taken through symplastic pathway and accumulates in specific tissues (Hall and Williams 2003), where it hampers metabolism (Van Assche and Clijsters 1990; Jonak et al. 2004). Being highly toxic in nature, cadmium induces severe damage to photosynthesis, water homeostasis, stomatal regulation, nutrient relation (Nazar et al. 2012), metabolism of auxin (Zou et al. 2012), chlorophyll contents (Hussain et al. 2013), and antioxidant defense system (Chen et al. 2003).

One or combination of these cadmium-induced hazards suppresses plant growth (Jonak et al. 2004).

Cadmium also induces higher synthesis of reactive oxygen species (ROS) such as hydrogen peroxide, singlet oxygen, hydroxyl, and superoxide radicals (Ashraf et al. 2012; Hussain et al. 2012). ROS are known to disintegrate lipids, proteins, pigments, DNA, and other macromolecules (Ashraf 2009). Higher cellular level of ROS also modifies plant antioxidant system which comprises antioxidant enzymes (superoxide dismutase, peroxidases, catalases, and glutathione reducatse) and non-enzymatic antioxidants (carotenoids, tocopherols, and ascorbic acid) (Ashraf

I. Hussain  M. A. Ashraf (&)  R. Rasheed  A. Asghar 

M. A. Sajid  M. Iqbal

Department of Botany, Government College University,

Faisalabad 38000, Pakistan e-mail: arsilpk@gmail.com 123

Braz. J. Bot

DOI 10.1007/s40415-014-0126-6 2009). Different methods can be used to reduce the uptake of Cd2? by plants, such as selecting metal-excluding plants (Wei et al. 2005), using soil amendments (Keller et al. 2005) and applying effective plant fertilization (Sarwar et al. 2010). However, in case of soil amendments and plant fertilization, plant growth stage could affect their effectiveness. Therefore, the degree of alleviation of metal stress in plants by these methods is not consistent.

Silicon is considered as essential element for plant growth and development (Epstein and Bloom 2005). It regulates nutrient relation of plants grown under environmental hazards. Addition of Si in the growth medium help plants to maintain the rigidity of cell walls when under stress (Hossain et al. 2007). It could increase light interception and net photosynthesis, and improve water-use efficiency (WUE) in different plants (Al-aghabary et al. 2004; Li et al. 2007). In addition, it remediates nutrient imbalance in plants and results in increased grain yield (Gao et al. 2006; Romero-Aranda et al. 2006; Liang et al. 2007). Furthermore, Si has been shown to reduce Cd2? uptake in plants (Shi et al. 2005) possibly by blocking the apoplastic pathway partially across the roots and alter the apoplastic transport of the Cd2? in plants (Rogalla and

Ronald 2002; Liang et al. 2007).

Wheat (Triticum aestivum L.) is well adapted to a wide range of soil and climatic conditions. However, being mobile and transported through apoplastic pathway, Cd2? accumulation in wheat tissues could affect the synthesis and transport of photoassimilates to developing sinks, thereby resulting in major grain yield losses in wheat. The translocation of Cd2? from root to shoot was positively associated with buildup of Cd2? in grains of wheat and rice (Greger and Lofstedt 2004). The Cd2? accumulation in grains could exert major threats to health. Therefore, the principle objective of the study was to assess whether Si application in the rooting medium at boot stage could affect the translocation of Cd2? in the wheat grains.

Materials and methods

Source of material and treatments

Seeds of two wheat cultivars, namely, AARI-2011 (Cdsensitive) and FSD-2008 (Cd-tolerant), were obtained from